It's hard, but provably not as hard. If you don't need the money, you can afford to take more and better risk with it.
More risk is enough to get this article (not even necessarily better risk) - if 100 people take a pure 100:1 bet, then 1 can get an article like this.
[As mentioned in the sibling comment, if you have enough time, then hard becomes easy]
It's almost certainly more challenging to take better risks as the investment requires gets larger. All sorts of new challenges crop up that didn't exist with smaller investments. It's the reason why companies have a harder and harder time sustaining the same growth rate as they get larger.
Within the stock market alone, you get access to the same exact risks as the people with the $10k YOLO accounts. If you look at WSB, you'll see a lot more posts about people posting losses on their YOLO accounts than posting massive wins. There are a lot of sharks swimming in the capital markets with deep expertise.
I would argue that you have proven my point - if I have a bunch of money, I can pay for expertise/management that is going to net me a higher return.
Not starting with $1 million. At $10 million you have to be the shark. You need to be closer to $100 million to be able to afford the sharks the don't have their own principal to work with. Even then, you still need to know how to hire the sharks.
Source: I used to work in this market.